Operator Successfully Trials Novel Cementing Technologies in a Deepwater Gulf of Mexico Exploration Well

Abstract

The objective of this paper is to present the planning, simulations, laboratory testing and operational results for the initial deepwater deployment of a new cementing technique which utilizes a "heat sweep" of warm seawater circulated inside the casing after cement placement to accelerate early compressive strength development. This technique is made possible through a novel stabbed-in inner string cementing technology which also reduces operational risk for the cement job and saves rig time by eliminating conventional cement shoe tracks. The pre-project planning included comprehensive thermal simulations for placement of the "heat sweep", the 22″ surface casing cement job's temperature profile over time and the corresponding effect on compressive strength development. Additional laboratory testing of the "rig-blend" cement to be used in the well was also completed with and without the effect of the "heat sweep" to finalize the wait-on-cement (WOC) criteria for the 22″ cement job. Finally, a set of detailed operational steps were formalized in the drilling program. The 1000 m (3281 ft) 22″ surface casing cement job at 1532 m (5026 ft) water depth was successful, and several best practices and lessons learned were recorded for the deployment of the new technologies. Highlights included preparing the "heat sweep" utilizing rig systems to the initial placement temperature of 75°C (167°F), cementing through the stabbed-in inner string system, placement of the "heat sweep" inside the casing, and recovering a downhole cement sample and temperature logger from the bottom-hole assembly (BHA). The downhole temperature logger recorded that a maximum 37.07°C (98.72°F) was delivered to the casing shoe, which was roughly double the maximum recorded environmental temperature and an exponential increase above the minimum environmental temperature, near freezing, at the mudline. The "heat sweep" generated approximately 9 times more compressive strength in the cement over 8 hours (1150.55 psi) when compared to the base case without the "heat sweep" effect (129.81 psi). This increase in compressive strength development was equivalent to a 4-hour WOC reduction to develop 100 psi in the tail slurry or a 16-hour reduction in WOC to develop 500 psi in the lead slurry near mudline. Additionally, the 22″ casing pressure tested to 2000 psi, and the shoe was drilled out in less than 20 minutes, saving 6 1/2 hours of rig time when compared to the Operator's most recent subsea well. The formation integrity test (FIT) achieved a slightly higher pressure than expected, and the subsequent 17 ½" section was drilled in a single fast run. The subject novel cementing technologies have the potential to reduce costs and drive efficiency for deepwater drilling operations. This case study presents the first deepwater application for utilizing heated seawater to help rapidly build compressive strength in a cement job after placement through a novel stabbed-in inner string cementing system.